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/* Copyright 2023 Remi Lehe
*
* This file is part of WarpX.
*
* License: BSD-3-Clause-LBNL
*/
#include "ChargeOnEB.H"
#include "Diagnostics/ReducedDiags/ReducedDiags.H"
#include "Utils/TextMsg.H"
#include "Utils/WarpXConst.H"
#include "Utils/Parser/ParserUtils.H"
#include "WarpX.H"
#include <AMReX_GpuAtomic.H>
#include <AMReX_Config.H>
#include <AMReX_Geometry.H>
#include <AMReX_MultiFab.H>
#include <AMReX_ParallelDescriptor.H>
#include <AMReX_ParmParse.H>
#include <AMReX_REAL.H>
#include <algorithm>
#include <fstream>
#include <vector>
using namespace amrex;
// constructor
ChargeOnEB::ChargeOnEB (std::string rd_name)
: ReducedDiags{rd_name}
{
// Only 3D is working for now
#if !(defined WARPX_DIM_3D)
WARPX_ALWAYS_ASSERT_WITH_MESSAGE(false,
"ChargeOnEB reduced diagnostics only works in 3D");
#endif
#if !(defined AMREX_USE_EB)
WARPX_ALWAYS_ASSERT_WITH_MESSAGE(false,
"ChargeOnEB reduced diagnostics only works when compiling with EB support");
#endif
// resize data array
m_data.resize(1, 0.0_rt);
// Read optional weighting
std::string buf;
const amrex::ParmParse pp_rd_name(rd_name);
m_do_parser_weighting = pp_rd_name.query("weighting_function(x,y,z)", buf);
if (m_do_parser_weighting) {
std::string weighting_string;
utils::parser::Store_parserString(
pp_rd_name,"weighting_function(x,y,z)", weighting_string);
m_parser_weighting = std::make_unique<amrex::Parser>(
utils::parser::makeParser(weighting_string,{"x","y","z"}));
}
if (ParallelDescriptor::IOProcessor())
{
if ( m_write_header )
{
// open file
std::ofstream ofs{m_path + m_rd_name + "." + m_extension, std::ofstream::out};
// write header row
int c = 0;
ofs << "#";
ofs << "[" << c++ << "]step()";
ofs << m_sep;
ofs << "[" << c++ << "]time(s)";
ofs << m_sep;
ofs << "[" << c++ << "]Charge (C)";
ofs << std::endl;
// close file
ofs.close();
}
}
}
// end constructor
// function that computes the charge at the surface of the EB
void ChargeOnEB::ComputeDiags (const int step)
{
// Judge whether the diags should be done
if (!m_intervals.contains(step+1)) { return; }
#if ((defined WARPX_DIM_3D) && (defined AMREX_USE_EB))
// get a reference to WarpX instance
auto & warpx = WarpX::GetInstance();
// Only compute the integral on level 0
int const lev = 0;
// get MultiFab data at lev
const amrex::MultiFab & Ex = warpx.getEfield_fp(lev,0);
const amrex::MultiFab & Ey = warpx.getEfield_fp(lev,1);
const amrex::MultiFab & Ez = warpx.getEfield_fp(lev,2);
// get EB structures
amrex::EBFArrayBoxFactory const& eb_box_factory = warpx.fieldEBFactory(lev);
amrex::FabArray<amrex::EBCellFlagFab> const& eb_flag = eb_box_factory.getMultiEBCellFlagFab();
amrex::MultiCutFab const& eb_bnd_cent = eb_box_factory.getBndryCent();
amrex::MultiCutFab const& eb_bnd_normal = eb_box_factory.getBndryNormal();
amrex::Array<const amrex::MultiCutFab*,AMREX_SPACEDIM> eb_area_fraction = eb_box_factory.getAreaFrac();
// get surface integration element
const amrex::GpuArray<amrex::Real,AMREX_SPACEDIM> dx = warpx.Geom(lev).CellSizeArray();
amrex::Real const dSx = dx[1]*dx[2];
amrex::Real const dSy = dx[2]*dx[0];
amrex::Real const dSz = dx[0]*dx[1];
// Required for parser
const amrex::RealBox& real_box = warpx.Geom(lev).ProbDomain();
const bool do_parser_weighting = m_do_parser_weighting;
auto fun_weightingparser =
utils::parser::compileParser<3>(m_parser_weighting.get());
// Integral to calculate
amrex::Gpu::Buffer<amrex::Real> surface_integral({0.0_rt});
amrex::Real* surface_integral_pointer = surface_integral.data();
// Loop over boxes
#ifdef AMREX_USE_OMP
#pragma omp parallel if (amrex::Gpu::notInLaunchRegion())
#endif
for (amrex::MFIter mfi(Ex, TilingIfNotGPU()); mfi.isValid(); ++mfi)
{
const amrex::Box & box = mfi.tilebox( amrex::IntVect::TheCellVector() );
// Skip boxes that do not intersect with the embedded boundary
// (i.e. either fully covered or fully regular)
amrex::FabType fab_type = eb_flag[mfi].getType(box);
if (fab_type == amrex::FabType::regular) continue;
if (fab_type == amrex::FabType::covered) continue;
// Extract data for electric field
const amrex::Array4<const amrex::Real> & Ex_arr = Ex.array(mfi);
const amrex::Array4<const amrex::Real> & Ey_arr = Ey.array(mfi);
const amrex::Array4<const amrex::Real> & Ez_arr = Ez.array(mfi);
// Extract data for EB
auto const& eb_flag_arr = eb_flag.array(mfi);
const amrex::Array4<const amrex::Real> & eb_bnd_normal_arr = eb_bnd_normal.array(mfi);
const amrex::Array4<const amrex::Real> & eb_bnd_cent_arr = eb_bnd_cent.array(mfi);
const amrex::Array4<const amrex::Real> & dSx_fraction_arr = eb_area_fraction[0]->array(mfi);
const amrex::Array4<const amrex::Real> & dSy_fraction_arr = eb_area_fraction[1]->array(mfi);
const amrex::Array4<const amrex::Real> & dSz_fraction_arr = eb_area_fraction[2]->array(mfi);
amrex::ParallelFor( box,
[=] AMREX_GPU_DEVICE (int i, int j, int k) {
// Only cells that are partially covered do contribute to the integral
if (eb_flag_arr(i,j,k).isRegular() || eb_flag_arr(i,j,k).isCovered()) return;
// Find nodal point which is outside of the EB
// (eb_normal points towards the *interior* of the EB)
int const i_n = (eb_bnd_normal_arr(i,j,k,0) > 0)? i : i+1;
int const j_n = (eb_bnd_normal_arr(i,j,k,1) > 0)? j : j+1;
int const k_n = (eb_bnd_normal_arr(i,j,k,2) > 0)? k : k+1;
// Find cell-centered point which is outside of the EB
// (eb_normal points towards the *interior* of the EB)
int i_c = i;
if ((eb_bnd_normal_arr(i,j,k,0)>0) && (eb_bnd_cent_arr(i,j,k,0)<=0)) i_c -= 1;
if ((eb_bnd_normal_arr(i,j,k,0)<0) && (eb_bnd_cent_arr(i,j,k,0)>=0)) i_c += 1;
int j_c = j;
if ((eb_bnd_normal_arr(i,j,k,1)>0) && (eb_bnd_cent_arr(i,j,k,1)<=0)) j_c -= 1;
if ((eb_bnd_normal_arr(i,j,k,1)<0) && (eb_bnd_cent_arr(i,j,k,1)>=0)) j_c += 1;
int k_c = k;
if ((eb_bnd_normal_arr(i,j,k,2)>0) && (eb_bnd_cent_arr(i,j,k,2)<=0)) k_c -= 1;
if ((eb_bnd_normal_arr(i,j,k,2)<0) && (eb_bnd_cent_arr(i,j,k,2)>=0)) k_c += 1;
// Compute contribution to the surface integral $\int dS \cdot E$)
amrex::Real local_integral_contribution = 0;
local_integral_contribution += Ex_arr(i_c,j_n,k_n)*dSx*(dSx_fraction_arr(i+1,j,k)-dSx_fraction_arr(i,j,k));
local_integral_contribution += Ey_arr(i_n,j_c,k_n)*dSy*(dSy_fraction_arr(i,j+1,k)-dSy_fraction_arr(i,j,k));
local_integral_contribution += Ez_arr(i_n,j_n,k_c)*dSz*(dSz_fraction_arr(i,j,k+1)-dSz_fraction_arr(i,j,k));
// Add weighting if requested by user
if (do_parser_weighting) {
// Get the 3D position of the centroid of surface element
amrex::Real x = (i + 0.5_rt + eb_bnd_cent_arr(i,j,k,0))*dx[0] + real_box.lo(0);
amrex::Real y = (j + 0.5_rt + eb_bnd_cent_arr(i,j,k,1))*dx[1] + real_box.lo(1);
amrex::Real z = (k + 0.5_rt + eb_bnd_cent_arr(i,j,k,2))*dx[2] + real_box.lo(2);
// Apply weighting
local_integral_contribution *= fun_weightingparser(x, y, z);
}
// Given that only a tiny fraction of the cells have a non-zero contribution
// (the ones that intersect with the EB), it is not clear whether ReduceOpSum
// or AtomicAdd would be faster. However, the implementation with AtomicAdd is easier.
amrex::HostDevice::Atomic::Add( surface_integral_pointer, local_integral_contribution );
});
}
// Reduce across MPI ranks
surface_integral.copyToHost();
amrex::Real surface_integral_value = *(surface_integral.hostData());
amrex::ParallelDescriptor::ReduceRealSum( surface_integral_value );
// save data
m_data[0] = PhysConst::ep0 * surface_integral_value;
#endif
}
// end void ChargeOnEB::ComputeDiags
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